CN108544077A - A Friction Stir Spot Welding Method with Friction Pre-stacked Intermediate Layer Assisted by Backfilling Heterogeneous Materials - Google Patents

Abstract

The invention discloses a friction-stacked intermediate layer assisted heterogeneous material backfilling friction stir spot welding method, which belongs to the field of welding technology. The technical points are as follows: during the welding process, the intermediate layer with metallurgical bonding with the lower plate is prepared by friction surfacing on the upper surface of the lower plate of the spot welding joint; The welding of the spot welding joint is completed under the condition of no direct contact with the lower plate. The invention significantly reduces the abrasion of the welding tool due to the high hardness of the material on one side of the joint during backfilling friction stir spot welding of heterogeneous joints, and effectively improves the metal-to-metal connection at the connection interface in backfilling friction stir spot welding of heterogeneous material joints. The occurrence of brittle phases such as compounds and defects such as pore cracks. The invention also has the advantages of simple process equipment, wide application range and high joint strength.

Description

A Friction Stir Spot Welding Method with Friction Pre-stacked Intermediate Layer Assisted by Backfilling Heterogeneous Materials

technical field

The invention relates to a method for backfilling friction stir spot welding of heterogeneous materials, in particular to a method of using friction stir surfacing technology to pre-stack an intermediate layer on the surface of hard materials in spot welding joints of heterogeneous materials to reduce the friction between hard materials and soft materials. The invention relates to a process method for wear of a welding tool in material friction stir spot welding, improving the structure of a joint, and increasing the strength of a lap joint, and belongs to the technical field of additive manufacturing.

Background technique

With the development of the times, people put forward higher requirements for the lightweight of industrial products in order to reduce energy consumption and improve energy efficiency. Achieving an efficient connection of heterogeneous materials helps to optimize the material structure of industrial products. The use of different materials for components with different mechanical properties can effectively reduce the overall quality of the product, reduce energy consumption, and improve energy efficiency. At the same time, it can effectively control costs and increase product life. However, the physical and chemical properties of heterogeneous materials are often quite different, and it is difficult to achieve effective connection through traditional fusion welding, resistance welding, etc., while diffusion welding, brazing and other welding methods are limited by equipment and difficult to achieve large-scale industrial Production. Backfill friction stir spot welding is one of the effective ways to solve the connection of dissimilar materials. Because it realizes the solid-phase connection of materials under the condition of large plastic deformation, and the connection temperature is not higher than the melting point of the base metal, it can effectively avoid welding such as pores, spatter, and thermal cracks that are common in traditional fusion welding and resistance welding when connecting dissimilar materials. defect. In addition, the backfill friction stir spot welding equipment has simple structure, short connection time and high production efficiency, so it is easy to realize large-scale production.

In the spot welding joints of dissimilar materials, when the method of backfilling friction stir welding is directly used to weld dissimilar materials, the contact between the welding tool and the hard material will easily cause the wear of the friction stir welding head. The existing solution is generally to customize the backfill friction stir welding tool with higher hardness, but this will increase the cost and is not conducive to actual industrial production. For example, the Chinese patent application number is 201610515613.8, which is named as a method for improving the strength of friction stir spot welding joints of titanium alloy/aluminum alloy dissimilar metals, and the above technical problems exist.

Contents of the invention

A brief overview of the invention is given below in order to provide a basic understanding of some aspects of the invention. It should be understood that this summary is not an exhaustive overview of the invention. It is not intended to identify key or critical parts of the invention nor to delineate the scope of the invention. Its purpose is merely to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

In view of this, the purpose of the present invention is to provide a friction pre-stacked intermediate layer assisted heterogeneous material backfilling friction stir spot welding method to solve the problems of welding head wear and heterogeneous joint strength when backfilling friction stir spot welding of heterogeneous materials problems, to achieve the purpose of uniform joint organization and reliable joint performance.

The present invention provides a friction stir spot welding method of friction pre-stacking intermediate layer assisted by heterogeneous material backfilling, specifically:

Step 1: Pretreat the surface of the material to be welded, remove the oxide film on the surface of the material to be welded, and clean the surface impurities on the treated surface to be welded;

Step 2: After the pretreatment, prepare the middle layer by means of friction stir surfacing welding on the surface of the hard material with the material to be welded in the middle layer;

Step 3: The spot welding joints of heterogeneous materials are formed into a joint form of hard material/intermediate layer/soft material from bottom to top, and joint welding is realized by backfilling friction stir spot welding.

Preferably, in step 1, the surface of the material to be welded is pretreated by one or more of the methods of pickling, sand blasting, machining, and mechanical grinding. The oxide film on the surface of the raw material used for the intermediate layer is removed.

Preferably, in step 1, the material to be welded from which the oxide film has been removed is placed in acetone or alcohol, ultrasonic cleaning is used to remove the residual particles in the pretreatment process, and the surface of the material to be welded is wiped with acetone or alcohol to remove oil and dirt before welding. dust.

Preferably, in step 2, the raw materials used for the surfacing middle layer are rods with a diameter of 10 mm to 75 mm.

Preferably, in step 2, the raw materials used for the surfacing intermediate layer can be steel, titanium and its alloys, aluminum and its alloys, zinc and its alloys, tin and its alloys, copper and its alloys, aluminum matrix composites, metal matrix composites One or more of materials and thermoplastic organic materials.

Preferably, in step 2, during the friction surfacing process of the intermediate layer, the surfacing raw material on the processing surface is in a plastic flow state, and a reinforcing phase is added.

Preferably, in step 2, the specific method of preparing the intermediate layer by means of friction stir surfacing is: clamp the raw materials used for the surfacing intermediate layer in a friction stir welding machine, and use a rotating speed of 600rpm to 5000rpm and a linear speed of 50mm on the surface of the hard material /min～300mm/min, pressing speed 0.3mm/s～15mm/s, inclination 0°～5°friction stir surfacing to prepare the middle layer.

Preferably, in step 2, the intermediate layer after friction surfacing can be selected for single, secondary or multiple surfacing according to production needs, and it is selected to perform or not perform secondary processing on the surfacing intermediate layer.

Preferably, in step 3, the backfilling friction stir spot welding is divided into a plunge-in stage, an intermediate stay stage, a backfill stage, and an evacuation stage.

Preferably, in step 3, the specific parameters of the backfill friction stir spot welding are: the maximum penetration depth of the stirring sleeve is not less than 0mm from the surface of the hard material, the maximum penetration depth of the stirring sleeve is not less than 0.05mm into the middle layer, and the rotation speed 600rpm～2500rpm, penetration and backfilling speed 0.2mm/s～1.5mm/s, intermediate residence time 1s～15s.

Beneficial effect:

The present invention pre-stacks the middle layer by using the method of friction stir surfacing welding on the surface of the hard material, and through the joint form of hard material/middle layer/soft material, so that in the process of backfilling friction stir spot welding, the welding tool and the hard There is no direct contact between heterogeneous materials, so that the connection of dissimilar material spot welding joints can be realized. The invention has no direct contact between the welding tool and the hard material during the welding process, so it effectively solves the wear problem of the welding tool in the backfill friction stir spot welding of heterogeneous materials, improves the joint structure, effectively improves the joint strength, and has a relatively high performance. High practical application value.

The invention realizes the effective overlapping of the friction stir welding between heterogeneous materials, reduces the abrasion of the friction stir welding head, reduces the manufacturing requirement and cost of the friction stir welding head, and is beneficial to the actual industrial production.

The friction surfacing welding intermediate layer raw material of the present invention has a wide selection range, and the required intermediate layer material can be selected according to the actual situation, and no harmful waste is generated during the processing, and it has environmental protection, high production efficiency, and brittle phases such as intermetallic compounds at the interface. The generation is suppressed and other advantages.

In the present invention, the processing temperature in the production process is always not higher than the melting point of the soft material, and the heat input is extremely low. In addition, during the processing process, the material undergoes recovery and recrystallization under the action of large deformation and heat input. Therefore, after forming, the material structure is uniform and the grains are fine, the interface structure is excellent, and the mechanical properties are good. Moreover, the two thermal-mechanical effects of friction surfacing and backfill friction stir spot welding on the interface of heterogeneous materials can effectively improve the interface morphology and joint structure, and at the same time increase the interface strength.

Compared with the Chinese patent application 201610515613.8 mentioned in the background technology, it has advantages, see the comparison table: comparison table

Description of drawings

Fig. 1 is the friction surfacing intermediate layer process schematic diagram of the present invention;

Fig. 2 is a schematic diagram of the backfill friction stir spot welding process of the present invention.

In the figure: 1- intermediate layer raw material rod; 2-hard material; 3-backing plate; 4-intermediate layer; 5-stirring pin; 6-stirring sleeve;

Detailed ways

Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual implementation are described in this specification. It should be understood, however, that in developing any such practical embodiment, many implementation-specific decisions must be made in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and those Restrictions may vary from implementation to implementation. Furthermore, it should be understood that development work, while potentially complex and time-consuming, would be a routine undertaking for those skilled in the art having the benefit of this disclosure.

Here, it should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the device structure and/or processing steps closely related to the solution according to the present invention are shown in the drawings, and the Other details not relevant to the present invention are described.

Embodiment 1: This embodiment is described in conjunction with Fig. 1 and Fig. 2. A friction-stacked aluminum alloy assisted backfill type friction stir spot welding aluminum/steel dissimilar metal joint is specifically implemented as follows:

Step 1: Pretreat the surface of the material to be welded, remove the oxide film on the surface of the material to be welded, and clean the surface impurities on the treated surface to be welded;

Step 2: After the pretreatment, prepare the middle layer by means of friction stir surfacing welding on the surface of the hard material with the material to be welded in the middle layer;

Step 3: The spot welding joints of heterogeneous materials are formed into a joint form of hard material/intermediate layer/soft material from bottom to top, and joint welding is realized by backfilling friction stir spot welding.

Embodiment 2: This embodiment is described in conjunction with FIG. 1 and FIG. 2. A friction-stacked aluminum alloy assisted backfill type friction stir spot welding aluminum/steel dissimilar metal joint is specifically implemented as follows:

Step 1: Use one or more methods of angle grinder, sandpaper grinding, and mechanical processing on the surface of the steel plate to be welded and the aluminum plate to be welded to remove the oxide film on the surface of the plate to be welded; the raw materials used for friction surfacing are processed by turning, The surface oxide film is removed by boring and milling; the pretreated surface of the material to be welded is ultrasonically cleaned with acetone or alcohol, and the surface impurities are wiped;

Step 2: After pretreatment, prepare the intermediate layer on the surface of the steel plate with the bar to be welded by friction stir surfacing; use milling and grinding to perform secondary processing on the intermediate layer, so that the thickness of the intermediate layer is 0.02mm～1.5mm.

Step 3: The dissimilar metal spot welding joints are formed into a joint form of hard material/intermediate layer/soft material from bottom to top, and the joint welding is realized by backfilling friction stir spot welding.

Wherein, the raw material used for the surfacing middle layer is one or more of aluminum alloy rods, copper alloy rods, and zinc alloy rods with a diameter of 10 mm to 75 mm.

Among them, during the friction surfacing process of the intermediate layer, the surfacing raw material on the processing surface is in a plastic flow state, and a reinforcing phase can be added. Therefore, a reinforcing phase can be added during the surfacing of the intermediate layer. In this embodiment, it is preferably one or more of SiC _p , TiC, Si ₃ N ₄ , SiO ₂ or TiB ₂ particles, graphene, and whiskers.

Furthermore, the raw materials used for the middle layer of surfacing are clamped in the friction stir welding machine, and the rotating speed is 600rpm~5000rpm, the line speed is 50mm/min~300mm/min, and the pressing speed is 0.3mm/s~15mm/s on the surface of the hard material. , The intermediate layer is prepared by friction stir surfacing welding with an inclination angle of 0°～5°.

Further, the specific parameters of backfill friction stir spot welding are: the maximum penetration depth of the stirring sleeve is not less than 0mm from the surface of the hard material, the maximum penetration depth of the stirring sleeve is not less than 0.05mm into the middle layer, and the rotation speed is 600rpm-2500rpm. The penetration and backfilling speed is 0.2mm/s～1.5mm/s, and the intermediate residence time is 1s～15s.

Embodiment 3: The steps and parameter ranges of this embodiment are the same as those of Embodiment 1 or 2. The difference is that the upper plate is made of magnesium alloy, the lower plate is made of low-carbon steel, and the middle layer is selected from one of magnesium alloy, zinc alloy and copper alloy. species or several.

Embodiment 4: This embodiment is the same as embodiment 1, 2 or 3 with the same steps and parameter ranges, but the difference is that the upper plate is made of aluminum alloy, the lower plate is made of titanium alloy, and the middle layer is made of aluminum alloy, titanium alloy or copper alloy. one or more of.

Embodiment 5: This embodiment is the same as Embodiment 1, 2, 3 or 4 with the same steps and parameter ranges, but the difference is that the upper plate is made of magnesium alloy, the lower plate is made of titanium alloy, and the middle layer is made of magnesium alloy, titanium alloy and copper alloy one or more of them.

Embodiment 6: This embodiment is identical with embodiment 1, 2, 3, 4 or 5 steps and parameter range, and difference is: upper plate selects aluminum alloy for use, and lower plate selects for use nickel alloy or cupronickel, and middle layer selects aluminum alloy, One or more of copper alloy and titanium alloy.

Although the embodiments disclosed in the present invention are as above, the content thereof is only for the convenience of understanding the technical solutions of the present invention, and is not intended to limit the present invention. Anyone skilled in the technical field to which the present invention belongs can make any modifications and changes in the form and details of implementation without departing from the core technical solution disclosed in the present invention, but the scope of protection defined by the present invention remains The scope defined by the appended claims shall prevail.

Claims (10)

1. A kind of friction pre-stacked middle layer auxiliary heterogeneous material backfill type friction stir spot welding method, it is characterized in that, concrete method is: Step 1: Pretreat the surface of the material to be welded, remove the oxide film on the surface of the material to be welded, and clean the surface impurities on the treated surface to be welded; Step 2: After the pretreatment, prepare the middle layer by means of friction stir surfacing welding on the surface of the hard material with the material to be welded in the middle layer; Step 3: The spot welding joints of heterogeneous materials are formed into a joint form of hard material/intermediate layer/soft material from bottom to top, and joint welding is realized by backfilling friction stir spot welding. 2. A kind of friction pre-stacked intermediate layer assisted heterogeneous material backfill type friction stir spot welding method according to claim 1, it is characterized in that, in step 1, the surface of the material to be welded is pretreated by pickling, spraying One or more of sand, machining, and mechanical grinding methods remove the oxide film on the surface of the hard material, soft material and raw material used for the surfacing intermediate layer to be welded. 3. A kind of friction pre-stacked intermediate layer assisted heterogeneous material backfilling friction stir spot welding method according to claim 2, characterized in that, in step 1, the material to be welded with the oxide film removed is placed in acetone or alcohol , Use ultrasonic cleaning to remove the residual particles in the pretreatment process, and use acetone or alcohol to wipe the surface of the material to be welded to remove oil and dust before welding. 4. The friction stir spot welding method according to claim 3, characterized in that, in step 2, the raw material used for the surfacing intermediate layer is a rod with a diameter of 10 mm to 75 mm . 5. A kind of friction pre-stacking intermediate layer assisted heterogeneous material backfilling friction stir spot welding method according to claim 4, characterized in that, in step 2, the raw materials used for the surfacing intermediate layer can be steel, titanium and alloys thereof One or more of aluminum and its alloys, zinc and its alloys, tin and its alloys, copper and its alloys, aluminum matrix composites, metal matrix composites, and thermoplastic organic materials. 6. A kind of friction pre-stacking intermediate layer assisted heterogeneous material backfilling type friction stir spot welding method according to claim 5, characterized in that, in step 2, in the process of friction surfacing intermediate layer, surfacing welding on the processing surface The raw material is in a plastic flow state, and the reinforcing phase is added. 7. A friction pre-stacking intermediate layer assisted heterogeneous material backfilling type friction stir spot welding method according to claim 6, characterized in that, in step 2, the specific method of preparing the intermediate layer by friction stir surfacing welding is: Clamp the raw materials used for the middle layer of surfacing in the friction stir welding machine, use the rotating speed of 600rpm to 5000rpm on the surface of the hard material, the linear speed of 50mm/min to 300mm/min, the pressing speed of 0.3mm/s to 15mm/s, and the inclination angle of 0 °～5°Friction stir surfacing to prepare the intermediate layer. 8. A kind of friction pre-stacking intermediate layer assisted heterogeneous material backfilling friction stir spot welding method according to claim 7, characterized in that, in step 2, the intermediate layer after friction surfacing can be selected according to production needs. Secondary, secondary or multiple surfacing, and choose to perform secondary processing on the intermediate layer of surfacing or not. 9. A friction pre-stacking intermediate layer assisted heterogeneous material backfilling friction stir spot welding method according to claim 8, characterized in that, in step 3, the backfilling friction stir spot welding is divided into a plunge-in stage and an intermediate stay phase, backfill phase, and evacuation phase. 10. A friction pre-stacking intermediate layer assisted heterogeneous material backfilling friction stir spot welding method according to claim 9, characterized in that, in step 3, the specific parameters of the backfilling friction stir spot welding are: the maximum pinch of the stirring sleeve The penetration depth is no less than 0mm from the hard material surface, the maximum penetration depth of the mixing sleeve into the middle layer is no less than 0.05mm, the rotation speed is 600rpm-2500rpm, the penetration and backfilling speed is 0.2mm/s～1.5mm/s, and the middle stay Time 1s ~ 15s.